The invention relates to a device and a method for trapping at least one microparticle in a fluid flow and an apparatus for arranging a plurality of microparticles in a fluid flow.
Biological assays, chemical tests, chemical synthesis, processing of samples or biological fluids may require processing microparticles. For example, processing microparticles carrying different analytes on their surface may allow for surface-based assays for detecting different types of analytes including (but not limited to) DNA sequences, antigens, lipids, proteins, peptides, hydrocarbons, toxins, chemical compounds or cells. Analysis on microparticles carrying analytes may be performed, for example, by optical or electrochemical monitoring, applying fluorescence, magnetism-based sensing, fluorescence quenching. Typically, microparticles suspended in fluids are trapped using optical tweezers, magnetism, dielectrophoresis, or mechanical traps. For example, mechanical traps integrated in microfluidic chips can be used for trapping single microparticles.
Dielectrophoresis relates to the motion of polarizable particles in a non-uniform or asymmetric electric field. In particular, microparticles subjected to an electric field become polarized and make up dipoles aligned to the applied field. In a non-uniform electric field, each half of the dipole experiences unequal Coulomb forces, and a net force is exerted on the microparticle. Depending on dielectric properties including structural, morphological and chemical characteristics, the microparticles respond differently to the applied asymmetric electric field.